Mouse Model Of Insulin Resistance Research Articles

404-P: Metformin Treatment Rescues Alterations of Insulin-Sensitive Glucose Transporters in the Lung of Insulin-Resistant Mice

Obesity and hyperglycemia have recently been identified as independent risk factors for the development of respiratory infections. Although the lung is a major organ to utilize glucose, the regulation of glucose transport in the healthy and diabetic lung has received little attention. We hypothesized that metformin would rescue diabetes-induced alterations of glucose transport in the lung. To test this hypothesis, we induced an insulin-resistant diabetic mouse model by feeding a high-fat diet for 16 weeks (n=10/group). A subset of mice was treated with metformin for 8 weeks. Protein content of class I glucose transporters (GLUTs -1, -2, -3, -4) and class III GLUTs (-8, -10, -12) was quantified by Western blotting in whole lung homogenates. Cell surface GLUTs were quantified using the biotinylated photolabeling technique. Glucose concentration in bronchoalveolar lavage (BAL) fluid was measured spectrophotometrically. After feeding a high-fat diet, mice became obese, mildly hyperglycemic, hyperinsulinemic, and insulin tolerant. Total protein content of GLUT4 and GLUT12 was significantly decreased in the lung of the insulin-resistant (IR) group (P <0.05). Following metformin treatment, protein content of GLUT4, but not GLUT12, was rescued in the lung of the treated IR mice (P <0.05). Cell-surface protein content of GLUT4 and GLUT8 was significantly decreased in the lung of IR mice, which was rescued in the treated group (P<0.05). IR mice demonstrated a trend towards a higher glucose concentration in the BAL fluid (P < 0.1). These novel findings suggest that 1) regulation of glucose transport is altered in the lung during obesity and hyperglycemia, potentially increasing the risk for pulmonary infection, and 2) metformin treatment rescues GLUT alterations in the lung of IR mice. Insights gained from this study could lead to the identification of significant metabolic therapeutic targets for diabetic patients affected by concurrent respiratory infections. Disclosure A. Campolo: None. Z. Maria: None. M. Hinsdale: None. L. Liu: None. V. Lacombe: None. Funding Harold Hamm Diabetes Center; National Institutes of Health

ApoAI-derived peptide increases glucose tolerance and prevents formation of atherosclerosis in mice

Aims/hypothesisFinding new treatment alternatives for individuals with diabetes with severe insulin resistance is highly desired. To identify novel mechanisms that improve glucose uptake in skeletal muscle, independently from insulin levels and signalling, we have explored the therapeutic potential of a short peptide sequence, RG54, derived from apolipoprotein A-I (ApoA-I).MethodsINS-1E rat clonal beta cells, C2C12 rat muscle myotubes and J774 mouse macrophages were used to study the impact of RG54 peptide on glucose-stimulated insulin secretion, glucose uptake and cholesterol efflux, respectively. GTTs were carried out on diet-induced insulin-resistant and Leprdb diabetic mouse models treated with RG54 peptide, and the impact of RG54 peptide on atherosclerosis was evaluated in Apoe−/− mice. Control mice received ApoA-I protein, liraglutide or NaCl.ResultsThe synthetic RG54 peptide induced glucose uptake in cultured muscle myotubes by a similar amount as insulin, and also primed pancreatic beta cells for improved glucose-stimulated insulin secretion. The findings were verified in diet-induced insulin-resistant and Leprdb diabetic mice, jointly confirming the physiological effect. The RG54 peptide also efficiently catalysed cholesterol efflux from macrophages and prevented the formation of atherosclerotic plaques in Apoe−/− mice.Conclusions/interpretationThe RG54 peptide exhibits good prospects for providing glucose control and reducing the risk of cardiovascular disease in individuals with severe insulin resistance.

Differential effects of diet- and genetically-induced brain insulin resistance on amyloid pathology in a mouse model of Alzheimer\u2019s disease

BackgroundBased on epidemiological and experimental studies, type 2 diabetes mellitus (T2DM), especially insulin resistance that comprises the core mechanism of T2DM, has been recognized as a significant risk factor for Alzheimer’s disease (AD). Studies in humans and diabetic AD model mice have indicated a correlation between insulin resistance and increased amyloid deposition in the brain. Paradoxically, mice with targeted disruption of genes involved in the insulin signaling pathway showed protective effects against the AD-related pathology. These conflicting observations raise an issue as to the relationship between dysregulation of insulin signaling and AD pathophysiology.MethodsTo study the causal relations and molecular mechanisms underlying insulin resistance-induced exacerbation of amyloid pathology, we investigated the chronological changes in the development of insulin resistance and amyloid pathology in two independent insulin-resistant AD mouse models, i.e., long-term high-fat diet (HFD) feeding and genetic disruption of Irs2, in combination with dietary interventions. In addition to biochemical and histopathological analyses, we examined the in vivo dynamics of brain amyloid-β (Aβ) and insulin by microdialysis technique.ResultsHFD-fed diabetic AD model mice displayed a reduced brain response to peripheral insulin stimulation and a decreased brain to plasma ratio of insulin during the hyperinsulinemic clamp. Diet-induced defective insulin action in the brain was accompanied by a decreased clearance of the extracellular Aβ in vivo and an exacerbation of brain amyloid pathology. These noxious effects of the HFD both on insulin sensitivity and on Aβ deposition in brains were reversibly attenuated by dietary interventions. Importantly, HFD feeding accelerated Aβ deposition also in the brains of IRS-2-deficient AD mice.ConclusionsOur results suggested a causal and reversible association of brain Aβ metabolism and amyloid pathology by diet-dependent, but not genetically-induced, insulin-resistance. These observations raise the possibility that the causal factors of insulin resistance, e.g., metabolic stress or inflammation induced by HFD feeding, but not impaired insulin signaling per se, might be directly involved in the acceleration of amyloid pathology in the brain.

Facile Fabrication of an Amentoflavone-Loaded Micelle System for Oral Delivery To Improve Bioavailability and Hypoglycemic Effects in KKAy Mice

In order to increase the oral bioavailability and antidiabetic effect of amentoflavone with multimechanisms, an oral micelle system was developed by using a N-vinyl pyrrolidone-maleate-guerbet alcohol monoester polymer for the first time, which was designated as P(NVP-MGAM)/AF. After oral administration, P(NVP-MGAM)/AF enhanced the oral bioavailability of amentoflavone, which was approximately 3.2 times that of amentoflavone solution. The animal study using the KKAy insulin-resistant diabetes mouse model indicated that it regulates the expression and activity of downstream signaling factors and proteins by lowering blood lipids, reducing inflammatory responses and activating the peroxisome proliferator-activated receptor (PPAR) γ signaling pathway and PI3K/Akt signaling pathway. After being made into micelles, it is more effective because of its better absorbability and bioavailability. The results from this study provide a theoretical basis for the clinical application of amentoflavone for diabetes treatment. The oral micelles of P(NVP-MGAM)/AF may become one of the most potent drugs in the treatment of diabetes mellitus, which opens up a new way for the prevention and treatment of diabetes.

Inhibition of Eph/ephrin interaction with the small molecule UniPR500 improves glucose tolerance in healthy and insulin-resistant mice

Eph/ephrin interactions and their bidirectional signaling are integral part of the complex communication system between β-cells, essential for glucose homeostasis. Indeed, Eph/ephrin system was shown to be directly involved in the glucose-stimulated insulin secretion (GSIS) process occurring in the pancreatic islets. Here we tested the Eph antagonist UniPR500 as GSIS enhancer.UniPR500 was validated as EphA5-ephrin-A5 inhibitor in vitro and its efficacy as GSIS enhancer was assessed on EndoC-βH1 cells. The selectivity of UniPR500 was evaluated by testing this compound on a panel of well-known molecular targets responsible for the regulation of glucose homeostasis. Plasmatic levels of UniPR500 were measured by HPLC/MS approach after oral administration. Finally, UniPR500 was tested as hypoglycemic agent in healthy mice, in a non-genetic mouse model of insulin resistance (IR) and in a non-genetic mouse model of type 1 diabetes (T1D).The compound is an orally bioavailable and selective Eph antagonist, able to increase GSIS from EndoC-βH1 cells. When tested in vivo UniPR500 showed to improve glucose tolerance in healthy and IR mice. As expected by a GSIS enhancer acting on healthy β-cells, UniPR500 was ineffective when tested on a non-genetic mouse model of type 1 diabetes, where pancreatic function was severely compromised.In conclusion our findings suggest that Eph targeting is a new and valuable pharmacological strategy in the search of new hypoglycemic agents.

Liver-specific insulin receptor isoform A expression enhances hepatic glucose uptake and ameliorates liver steatosis in a mouse model of diet-induced obesity.

ABSTRACTAmong the main complications associated with obesity are insulin resistance and altered glucose and lipid metabolism within the liver. It has previously been described that insulin receptor isoform A (IRA) favors glucose uptake and glycogen storage in hepatocytes compared with isoform B (IRB), improving glucose homeostasis in mice lacking liver insulin receptor. Thus, we hypothesized that IRA could also improve glucose and lipid metabolism in a mouse model of high-fat-diet-induced obesity. We addressed the role of insulin receptor isoforms in glucose and lipid metabolism in vivo. We expressed IRA or IRB specifically in the liver by using adeno-associated viruses (AAVs) in a mouse model of diet-induced insulin resistance and obesity. IRA, but not IRB, expression induced increased glucose uptake in the liver and muscle, improving insulin tolerance. Regarding lipid metabolism, we found that AAV-mediated IRA expression also ameliorated hepatic steatosis by decreasing the expression of Fasn, Pgc1a, Acaca and Dgat2 and increasing Scd-1 expression. Taken together, our results further unravel the role of insulin receptor isoforms in hepatic glucose and lipid metabolism in an insulin-resistant scenario. Our data strongly suggest that IRA is more efficient than IRB at favoring hepatic glucose uptake, improving insulin tolerance and ameliorating hepatic steatosis. Therefore, we conclude that a gene therapy approach for hepatic IRA expression could be a safe and promising tool for the regulation of hepatic glucose consumption and lipid metabolism, two key processes in the development of non-alcoholic fatty liver disease associated with obesity.This article has an associated First Person interview with the first author of the paper.

Suppression of Prolactin Secretion Partially Explains the Antidiabetic Effect of Bromocriptine in ob/ob Mice.

Previous studies have shown that bromocriptine mesylate (Bromo) lowers blood glucose levels in adults with type 2 diabetes mellitus; however, the mechanism of action of the antidiabetic effects of Bromo is unclear. As a dopamine receptor agonist, Bromo can alter brain dopamine activity affecting glucose control, but it also suppresses prolactin (Prl) secretion, and Prl levels modulate glucose homeostasis. Thus, the objective of the current study was to investigate whether Bromo improves insulin sensitivity via inhibition of Prl secretion. Male and female ob/ob animals (a mouse model of obesity and insulin resistance) were treated with Bromo and/or Prl. Bromo-treated ob/ob mice exhibited lower serum Prl concentration, improved glucose and insulin tolerance, and increased insulin sensitivity in the liver and skeletal muscle compared with vehicle-treated mice. Prl replacement in Bromo-treated mice normalized serum Prl concentration without inducing hyperprolactinemia. Importantly, Prl replacement partially reversed the improvements in glucose homeostasis caused by Bromo treatment. The effects of the Prl receptor antagonist G129R-hPrl on glucose homeostasis were also investigated. We found that central G129R-hPrl infusion increased insulin tolerance of male ob/ob mice. In summary, our findings indicate that part of Bromo effects on glucose homeostasis are associated with decrease in serum Prl levels. Because G129R-hPrl treatment also improved the insulin sensitivity of ob/ob mice, pharmacological compounds that inhibit Prl signaling may represent a promising therapeutic approach to control blood glucose levels in individuals with insulin resistance.

STAT1 Ablation in CD11c+ Cells Protects Mice from Obesity-Induced Insulin Resistance

Background: Obesity is a global epidemic and major risk factor for insulin resistance and type 2 diabetes. Obesity is associated with low grade chronic inflammation of adipose tissue (AT). F4/80+CD11c+ macrophages/dendritic cells are increased and polarized into M1-like phenotypes in AT and may contribute to insulin resistance in mouse models of obesity. STAT1 is a transcription factor that play key roles in macrophage polarization into M1-like phenotypes. Hence, we investigated the role of CD11c+ macrophage/dendritic cell STAT1 in obesity-induced AT inflammation and insulin resistance. Methods: Mice with specific knockout of STAT1 in CD11c+ cells were generated by crossbreeding STAT1 fl/fl and CD11c-Cre mice. CD11c/STAT1 KO and littermate controls were fed either high fat diet (HFD, for 16 weeks) to induce obesity or normal diet (ND) as lean controls. We evaluated body composition, insulin sensitivity, gene expression of inflammatory markers, various immune cells and brown/beige adipogenesis markers in AT. Results: Perigonadal white AT (PWAT) and body weight were not significantly different between KO and control groups but liver weight and liver-to-body weight ratio were significantly reduced in obese KO mice (p<0.05). STAT1 KO mice on HFD exhibited improved insulin sensitivity examined by insulin tolerance test (p<0.05) and reduced expression of inflammatory markers TNFα, IFNγ, IL-12 and MCP1 in PWAT and subcutaneous AT (SAT) compared to littermate controls (p<0.05). AT immune cell analysis revealed that STAT1 ablation caused a decrease in M1-like proinflammatory polarization and increase in M2-like polarization of F4/80+ macrophages, reduced number of total CD3+ T cells and CD8+T cells in PWAT. In addition, brown/beige adipogenesis markers UCP1, CIDEA and Prdm16 also upregulated (p<0.05) in SAT of obese KO mice. Conclusion: Our results show the critical role of macrophage/dendritic cell STAT1 in obesity-induced AT inflammation and insulin resistance. Disclosure A. Kalathookunnel Antony: None. X.D. Perrard: None. Z. Lian: None. J. Perrard: None. L. Hennighausen: None. C.W. Smith: None. C.M. Ballantyne: Research Support; Self; Abbott, Amarin Corporation, Amgen Inc., Esperion Therapeutics, Ionis Pharmaceuticals, Inc., Novartis Pharmaceuticals Corporation, Pfizer Inc., Regeneron Pharmaceuticals, Inc., Roche Diagnostics Corporation, Sanofi. Consultant; Self; Abbott, Amarin Corporation, Amgen Inc., AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Eli Lilly and Company, Esperion Therapeutics, Ionis Pharmaceuticals, Inc., Matinas BioPharma, Merck & Co., Inc., Novartis Pharmaceuticals Corporation, Novo Nordisk Inc., Pfizer Inc., Regeneron Pharmaceuticals, Inc., Roche Diagnostics Corporation, Sanofi. H. Wu: None.

2466 MicroRNA-451: A potential key player in the development of diabetic nephropathy in an insulin resistant mouse model

OBJECTIVES/SPECIFIC AIMS: MicroRNAs (miRNA) affect transcription of a number of genes involved in the development and progression of diabetic nephropathy (DN), and have become attractive therapeutic targets and biomarkers. Elevated renal gluconeogenesis, fibrosis, and albuminuria are early markers of incipient DN. Recent studies report that renal miRNA-451 may protect against DN and reduce renal gluconeogenesis in rodent models. MiRNA-451 is thought to act by targeting select factors resulting from disrupted insulin and growth factor signaling and the mechanistic-target of rapamycin (mTOR) in early DN. This study aimed to elucidate the role of miRNA-451 in the development and progression of DN. METHODS/STUDY POPULATION: To further elucidate the role of miRNA-451 in DN, we placed male insulin-resistant, TALLYHO/Jng mice on a high-fat diet (60% kCal). The mice were divided into 2 treatment groups and received 8 consecutive weekly intraperitoneal injections of locked nucleic acid (LNA) miR-451-inhibitor or LNA-scrambled compound (2 mg/kg·bw; n=8/treatment). Mice were euthanized after 12 weeks (4 weeks sans injections) and kidneys, liver, pancreas and abdominal adipose tissue were harvested for analysis. RESULTS/ANTICIPATED RESULTS: Renal homogenate expression of miRNA-451 was drastically reduced in inhibitor-treated mice (~6-fold) in comparison with scramble-treated mice. Western blotting of cortex homogenates for indicators of fibrosis and targets of miRNA-451 revealed a significant reduction in collagen IV (marker of epithelial integrity) in inhibitor-treated mice. In addition, metalloproteinase type 9 (MMP9, a known type IV collagenase), YWHAZ (a scaffolding protein and known target of miR-451), mTOR, and fructose bisphosphatase (FBP1, a rate-limiting gene in gluconeogenesis) were significantly increased in this group in comparison to scramble-treated mice. However, no differences were found in protein levels for glucose-6-phosphatase (G-6-Pase) or phosphoenolpyruvate (PEPCK), 2 additional gluconeogenic rate-limiting genes. MiRNA-451 antagonist did not significantly affect final body weight or blood glucose; however, mean blood sodium concentrations were slightly, but significantly higher (2%) in the LNA-inhibitor treated group (when compared with the scramble-treated group). No differences in blood potassium or chloride were found. Anion gap was 90% higher in the LNA-inhibitor treated group when compared with scramble-treated mice. No differences in urinary albumin to creatinine ratio were found between the two treatment groups. However, Masson Trichrome scoring revealed a 59% increase in fibrosis in inhibitor-treated mice. DISCUSSION/SIGNIFICANCE OF IMPACT: Collectively, these findings support a potentially protective role of miRNA-451 in attenuating signaling via mTOR that may alter both renal gluconeogenic potential (contributing to the diabetic phenotype) and activation and progression of renal fibrosis. Therapies to enhance miRNA-451 signaling may be beneficial to reduce renal pathology associated with DN.

Renal impact of systemic inhibition of miRNA‐451 in a mouse model of insulin resistance

MicroRNAs (miRNA) affect transcription of a number of genes involved in the development and progression of diabetic nephropathy (DN), and have become attractive therapeutic targets and biomarkers. Elevated renal gluconeogenesis, fibrosis, and albuminuria are early markers of incipient DN. Recent studies report that renal miRNA‐451 may protect against DN and reduce renal gluconeogenesis in rodent models. It is hypothetically thought to act by targeting select factors resulting from disrupted insulin and growth factor signaling and the mechanistic‐target of rapamycin (mTOR) in early DN. To further elucidate the role of miRNA‐451 in DN, we placed male insulin‐resistant, TALLYHO/Jng mice on a high‐fat diet (60% kCal). The mice were divided into two treatment groups and received 8 consecutive weekly intraperitoneal injections of locked nucleic acid (LNA) miR‐451‐inhibitor or LNA‐scrambled compound (2 mg/kg·bw; n = 8/treatment). Mice were euthanized after 12 weeks (4 weeks sans injections). Renal expression of miRNA‐451 was drastically reduced in inhibitor treated mice (~6‐fold) in comparison to scramble‐treated mice. Western blotting of cortex homogenates for indicators of fibrosis and targets of miRNA‐451 revealed a significant reduction in collagen IV (marker of epithelial integrity) in inhibitor treated mice. In addition, metalloproteinase type 9 (MMP9, a known type IV collagenase), YWHAZ (a scaffolding protein and known target of miR‐451), mTOR, and fructose bisphosphatase (FBP1, a rate‐limiting gene in gluconeogenesis) were significantly increased in this group in comparison to scramble‐treated mice. However, no differences were found in protein levels for glucose‐6‐phosphatase (G‐6‐Pase) or phosphoenolpyruvate (PEPCK), 2 additional gluconeogenic rate‐limiting genes. MiRNA‐451 antagonist did not significantly affect final body weight or blood glucose; however, mean blood sodium concentrations were slightly, but significantly higher (2%) in the LNA‐inhibitor treated group (when compared to the scramble‐treated group). No differences in blood potassium or chloride were found. Anion gap was 90% higher in the LNA‐inhibitor treated group when compared to scramble‐treated mice. No differences in urinary albumin to creatinine ratio were found between the two treatment groups. However, Masson's Trichrome scoring revealed a 59% increase in fibrosis in inhibitortreated mice. Overall, these studies support a potentially protective role of miRNA‐451 in attenuating signaling via mTOR that may alter both renal gluconeogenic potential (contributing to the diabetic phenotype) and activation and progression of renal fibrosis. Therapies to enhance miRNA‐451 signaling may be beneficial to reduce renal pathology associated with DN.Support or Funding InformationResearch reported in this abstract was supported by the National Center For Advancing Translational Sciences of the National Institutes of Health under Award Number TL1TR001431 and the Georgetown University Department of Medicine. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of HealthThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Tissue expression of DPP-IV in obesity-diabetes and modulatory effects on peptide regulation of insulin secretion

Dipeptidyl peptidase type 4 (DPP-4) inhibitors represent an important class of glucose-lowering drug for type 2 diabetes. DPP-4 enzyme activity has been observed to be significantly altered in type 2 diabetes. Here, the role of DPP-4 was examined in a high fat fed (HFF) mouse model of insulin resistance. HFF mice had an increased bodyweight (p < .01), were hyperglycaemic (p < .01) and hyperinsulinaemic (p < .05). Compared to normal diet, HFF mice exhibited increased plasma DPP-4 activity (p < .01). Tissue distribution patterns in lean and HFF mice demonstrated highest levels of DPP-4 activity in lung (20–26 μmol/min/mg protein) and small intestine (13–14 μmol/min/mg protein), and lowest activity in the spleen (3.8 μmol/min/mg protein). Modulation of DPP-4 activity by high fat feeding was observed in several tissues with increases in the lung (p < .05), liver (p < .05), kidney (p < .05) and pancreas (p < .05). With a high fat diet, DPP-4 gene expression was upregulated in the liver (p < .001) and downregulated in the pancreas (p < 0.001) and small intestine (p < .001). Immunohistochemical analysis revealed increased DPP-4 immunostaining localised primarily in the pancreatic islets of HFF mice (p < .01) with no change in islet GLP-1 expression. Treatment of HFF mice with metformin for 21-days resulted in inhibition of circulating DPP-4 activity (p < .05), decreased blood glucose (p < .05) and increased GLP-1 gene expression (p < .001). These data indicate that DPP-4 is modulated in a tissue specific manner and is dependent on physiological conditions such as hyperglycaemia and insulin resistance, suggesting a significant role in disorders such as diabetes.

Preventive effects of Salvia officinalis leaf extract on insulin resistance and inflammation in a model of high fat diet-induced obesity in mice that responds to rosiglitazone.

BackgroundSalvia officinalis (sage) is a native plant to the Mediterranean region and has been used for a long time in traditional medicine for various diseases. We investigated possible anti-diabetic, anti-inflammatory and anti-obesity effects of sage methanol (MetOH) extract in a nutritional mouse model of obesity, inflammation and insulin resistance, as well as its effects on lipolysis and lipogenesis in 3T3-L1 cells.MethodsDiet-induced obese (DIO) mice were treated for five weeks with sage methanol extract (100 and 400 mg kg−1/day bid), or rosiglitazone (3 mg kg−1/day bid), as a positive control. Energy expenditure, food intake, body weight, fat mass, liver glycogen and lipid content were evaluated. Blood glucose, and plasma levels of insulin, lipids leptin and pro- and anti-inflammatory cytokines were measured throughout the experiment. The effects of sage MetOH extract on lipolysis and lipogenesis were tested in vitro in 3T3-L1 cells.ResultsAfter two weeks of treatment, the lower dose of sage MetOH extract decreased blood glucose and plasma insulin levels during an oral glucose tolerance test (OGTT). An insulin tolerance test (ITT), performed at day 29 confirmed that sage improved insulin sensitivity. Groups treated with low dose sage and rosiglitazone showed very similar effects on OGTT and ITT. Sage also improved HOMA-IR, triglycerides and NEFA. Treatment with the low dose increased the plasma levels of the anti-inflammatory cytokines IL-2, IL-4 and IL-10 and reduced the plasma level of the pro-inflammatory cytokines IL-12, TNF-α, and KC/GRO. The GC analysis revealed the presence of two PPARs agonist in sage MetOH extract. In vitro, the extract reduced in a dose-related manner the accumulation of lipid droplets; however no effect on lipolysis was observed.ConclusionsSage MetOH extract at low dose exhibits similar effects to rosiglitazone. It improves insulin sensitivity, inhibits lipogenesis in adipocytes and reduces inflammation as judged by plasma cytokines. Sage presents an alternative to pharmaceuticals for the treatment of diabetes and associated inflammation.

The biological effects of the hypolipidaemic drug probucol microcapsules fed daily for 4weeks, to an insulin-resistant mouse model: potential hypoglycaemic and anti-inflammatory effects.

Probucol (PB) is an hypolipidaemic drug with potential antidiabetic effects. We showed recently using in vitro studies that when PB was incorporated with stabilising lipophilic bile acids and microencapsulated using the polymer sodium alginate, the microcapsules showed good stability but poor and irregular PB release. This suggests that PB microcapsules may exhibit better release profile and hence better absorption, if more hydrophilic bile acids were used, such as ursodeoxycholic acid (UDCA). Accordingly, this study aimed to produce PB-UDCA microcapsules and examine PB absorption and antidiabetic effects in our mouse-model of insulin-resistance and diabetes (fed high-fat diet; HFD). The study also aimed to examine the effects of the microcapsules on the bile acid profile. Healthy mice (fed low-fat diet; LFD) were used as control. Seventy mice were randomly allocated into seven equal groups: LFD, HFD given empty microcapsules, HFD given metformin (M), HFD given standard-dose probucol (PB-SD), HFD given high-dose probucol (PB-H), HFD given UDCA microcapsules and HFD given PB-UDCA microcapsules. Blood glucose (BG), inflammatory biomarkers (TNF-α, IFN-γ, IL-1β, IL-6, IL-10, IL-12 and IL-17), plasma cholesterol, non-esterified fatty acids and triglycerides were analysed together with plasma bile acid and probucol concentrations. PB-UDCA microcapsules reduced BG in HFD mice, but did not reduce inflammation or improve lipid profile, compared with positive control (HFD) group. Although PB-UDCA microcapsules did not exert hypolipidaemic or antiinflammatory effects, they resulted in significant hypoglycaemic effects in a mouse model of insulin resistance, which suggests potential applications in insulin-resistance and glucose haemostasis.

Inhibition of Interleukin-1 Receptor-Associated Kinases 1/4, Increases Gene Expression and Serum Level of Adiponectin in Mouse Model of Insulin Resistance.

Insulin resistance is a feature of most patients with type 2 diabetes mellitus. Epidemiological evidence suggest a correlation between inflammation and insulin resistant states such as obesity, but the underlying mechanisms are largely unknown. Interleukin-1 receptor-associated kinases (IRAK) play a central role in inflammatory responses by regulating the expression of various inflammatory genes in immune cells. This study was aimed to investigate the effect of IRAK inhibitor on gene transcription and serum concentration of adiponectin in insulin-resistant mice. Experimental mice were randomly divided into 6 groups: the healthy control group was fed a regular chow diet while other groups were fed with a high-fat diet for 12 weeks. After this period, the animals were treated with IRAK inhibitor, pioglitazone, both IRAK and pioglitazone, and DMSO, for two weeks. Adiponectin gene expression level was analyzed by real-time PCR. Additionally, serum adiponectin levels were measured by ELISA. Homeostasis model assessment-adiponectin (HOMA-AD) as an insulin sensitivity index was calculated. IRAK inhibitor and pioglitazone increased significantly the expression of adiponectin gene. Also, adiponectin concentration in the control group (9.67±1.1 μg/ml) increased to 25.34±2.04 μg/ml in pioglitazone treatment group. IRAK inhibitor also increased adiponectin concentration (18.24±1.53 μg/ml) but did not show a synergistic effect with pioglitazone when administered simultaneously (26.66±2.5 μg/ml). HOMA-AD was 0.33±0.04 in pioglitazone treated group, 0.6±0.13 in IRAK inhibitor group, and 0.31±0.03 in animals that received IRAKi and pioglitazone. Our findings suggest that increased adiponectin secretion from adipose tissue mediated by IRAK inhibitor may increase the insulin sensitivity in an animal model of insulin resistance.

Effects of high-fat diet and AMP-activated protein kinase modulation on the regulation of whole-body lipid metabolism

Metabolic flexibility, the capacity to adapt to fuel availability for energy production, is crucial for maintaining whole-body energy homeostasis. An inability to adequately promote FA utilization is associated with lipid accumulation in peripheral tissues and contributes to the development of insulin resistance. In vivo assays to quantify whole-body lipid oxidation in mouse models of insulin resistance are lacking. We describe a method for assessing whole-body FA oxidation in vivo, as well as tissue-specific lipid uptake in conscious mice. The method relies on intravenous administration of [9,10-3H(N)]palmitic acid combined with a non-β-oxidizable palmitate analog, [1-14C]2-bromopalmitic acid. Pretreatment with etomoxir, a CPT1 inhibitor that prevents the shuttling of FAs into mitochondria, markedly reduced the appearance of the β-oxidation product 3H2O in circulation and reduced lipid uptake by oxidative tissues including heart and soleus muscle. Whole-body fatty oxidation was unaltered between chow- or high-fat-fed WT and transgenic mice expressing a mutant form of the AMPK γ3 subunit (AMPKγ3R225Q) in skeletal muscle. High-fat feeding increased lipid oxidation in WT and AMPKγ3R225Q transgenic mice. In conclusion, this technique allows for the assessment of the effect of pharmaceutical agents, as well as gene mutations, on whole-body FA oxidation in mice.

The effect of ginger soy milk (Sulehe) combination on histopathology of pancreas and muscle of mouse model of insulin resistance

The effect of ginger soy milk (Sulehe) combination on histopathology of pancreas and muscle of mouse model of insulin resistance

Blood-Brain Barrier Dysfunction Precedes Cognitive Decline and Neurodegeneration in Diabetic Insulin Resistant Mouse Model: An Implication for Causal Link.

Diabetic insulin resistance and pro-diabetic diet are reported to increase dementia risk through unknown mechanisms. Emerging evidence suggests that the integrity of blood-brain barrier (BBB) is central to the onset and progression of neurodegeneration and cognitive impairment. Therefore, the current study investigated the effect of pro-diabetic diets on cognitive dysfunction in association to BBB integrity and its putative mechanisms. In C57BL/6J mice chronically ingested with a diet enriched in fat and fructose (HFF), Morris Water Maze (MWM) test indicated no significant cognitive decline after 4 weeks of HFF feeding compared to low-fat (LF) fed control. However, at this stage, BBB dysfunction accompanied by heightened neuroinflammation in cortex and hippocampal regions was already evident. After 24 weeks, HFF fed mice showed significantly deteriorated cognitive function concomitant with substantial neurodegeneration, which both showed significant associations with increased BBB permeability. In addition, the data indicated that the loss of BBB tight junctions was significantly associated with heightened inflammation and leukocyte infiltration. The data collectively suggest that in mice maintained on pro-diabetic diet, the dysfunctional BBB associated to inflammation and leukocyte recruitment precedes the neurodegeneration and cognitive decline, possibly indicating causal association.

Involvement of the metabolic sensor GPR81 in cardiovascular control.

GPR81 is a receptor for the metabolic intermediate lactate with an established role in regulating adipocyte lipolysis. Potentially novel GPR81 agonists were identified that suppressed fasting plasma free fatty acid levels in rodents and in addition improved insulin sensitivity in mouse models of insulin resistance and diabetes. Unexpectedly, the agonists simultaneously induced hypertension in rodents, including wild-type, but not GPR81-deficient mice. Detailed cardiovascular studies in anesthetized dogs showed that the pressor effect was associated with heterogenous effects on vascular resistance among the measured tissues: increasing in the kidney while remaining unchanged in hindlimb and heart. Studies in rats revealed that the pressor effect could be blocked, and the renal resistance effect at least partially blocked, with pharmacological antagonism of endothelin receptors. In situ hybridization localized GPR81 to the microcirculation, notably afferent arterioles of the kidney. In conclusion, these results provide evidence for a potentially novel role of GPR81 agonism in blood pressure control and regulation of renal vascular resistance including modulation of a known vasoeffector mechanism, the endothelin system. In addition, support is provided for the concept of fatty acid lowering as a means of improving insulin sensitivity.

The GLP-1 analogue lixisenatide decreases atherosclerosis in insulin-resistant mice by modulating macrophage phenotype.

Recent clinical studies indicate that glucagon-like peptide-1 (GLP-1) analogues prevent acute cardiovascular events in type 2 diabetes mellitus but their mechanisms remain unknown. In the present study, the impact of GLP-1 analogues and their potential underlying molecular mechanisms in insulin resistance and atherosclerosis are investigated. Atherosclerosis development was evaluated in Apoe -/- Irs2 +/- mice, a mouse model of insulin resistance, the metabolic syndrome and atherosclerosis, treated with the GLP-1 analogues lixisenatide or liraglutide. In addition, studies in Apoe -/- Irs2 +/- mice and mouse-derived macrophages treated with lixisenatide were performed to investigate the potential inflammatory intracellular pathways. Treatment of Apoe -/- Irs2 +/- mice with either lixisenatide or liraglutide improved glucose metabolism and blood pressure but this was independent of body weight loss. Both drugs significantly decreased atheroma plaque size. Compared with vehicle-treated control mice, lixisenatide treatment generated more stable atheromas, with fewer inflammatory infiltrates, reduced necrotic cores and thicker fibrous caps. Lixisenatide-treated mice also displayed diminished IL-6 levels, proinflammatory Ly6Chigh monocytes and activated T cells. In vitro analysis showed that, in macrophages from Apoe -/- Irs2 +/- mice, lixisenatide reduced the secretion of the proinflammatory cytokine IL-6 accompanied by enhanced activation of signal transducer and activator of transcription (STAT) 3, which is a determinant for M2 macrophage differentiation. STAT1 activation, which is essential for M1 phenotype, was also diminished. Furthermore, atheromas from lixisenatide-treated mice showed higher arginase I content and decreased expression of inducible nitric oxide synthase, indicating the prevalence of the M2 phenotype within plaques. Lixisenatide decreases atheroma plaque size and instability in Apoe -/- Irs2 +/- mice by reprogramming macrophages towards an M2 phenotype, which leads to reduced inflammation. This study identifies a critical role for this drug in macrophage polarisation inside plaques and provides experimental evidence supporting a novel mechanism of action for GLP-1 analogues in the reduction of cardiovascular risk associated with insulin resistance.

Tetrahydrobiopterin activates brown adipose tissue and regulates systemic energy metabolism.

Brown adipose tissue (BAT) is a central organ that acts to increase energy expenditure; its regulatory factors could be clinically useful in the treatment of obesity. Tetrahydrobiopterin (BH4) is an essential cofactor of tyrosine hydroxylase and nitric oxide synthase (NOS). Although BH4 regulates the known regulatory factors of BAT, such as noradrenaline (NA) and NO, participation of BH4 in BAT function remains unclear. In the present study, we investigate the role of BH4 in the regulation of BAT. Hph-1 mice, a mouse model of BH4 deficiency, exhibit obesity, adiposity, glucose intolerance, insulin resistance, and impaired BAT function. Impaired BAT function was ameliorated together with systemic metabolic disturbances by BAT transplantation from BH4-sufficient mice (control mice) into BH4-deficient mice, strongly suggesting that BH4-induced BAT has a critical role in the regulation of systemic energy metabolism. Both NA derived from the sympathetic nerve and NO derived from endothelial NOS in the blood vessels participate in the regulation of BH4. In addition, a direct effect of BH4 in the stimulation of brown adipocytes via NO is implicated. Taken together, BH4 activates BAT and regulates systemic energy metabolism; this suggests an approach for metabolic disorders, such as obesity and diabetes.